Oscillators are types of electronic circuits that generate repetitive, oscillating signals. Oscillators are used in a variety of electronic devices for a wide range of uses including timing, clock signals, communication signals, modulation signals, and the like.
Generally, oscillator circuits are designed to provide a specific signal at a selected frequency. The type of signal depends on the device using it. The selected frequency can be static or can vary over time, also depending on the device using the oscillation signal.